The pathogenesis of acute non-cardiogenic edematous lung injury (as occurs in Adult Repsiratory Distress Syndrome (ARDS), pulmonary O2 toxicity and other important lung disorders) is poorly understood but has two key features which are accumulation of neutrophils in the lung and injury to pulmonary vascular endothelium. Evidence now exists that influx and activation of neutrophils contributes directly to experimental edematous lung injury, but the mechanisms by which neutrophils might mediate endothelial damage and lung edema are unknown. We hypothesized that activated neutrophils adhere and release toxic O2 radical which damage endothelium and lead to edematous lung injury. Our findings in pulmonary O2 toxicity - a good model of edematous lung injury - supported this premise by showing that hyperoxia stimulated alveolar macrophages to make factors which attract neutrophils and stimulate thier adherence and release of O2 radicals. Additional support comes from he observation that stimulated normal but not O2 radical deficient CGD neutrophils damaged an isolated lung. We now plan to investigate the capacity of neutrophils and O2 radicals to damage endothelial cells and cause edematous lung injury in the saline-perfused isolated lung and cultured endothelial cells. This dual approach is needed to demonstrate specific cell injury which has significant physiologic consequences. Our immediate objectives are 1) to determine if O2 radicals from neutrophils damage endothelial cells and cause edematous injury in the isolated lung, and 2) to determine if O2 radicals from neutrophils damage endothelial cells in culture. We will add neutrophils and neutrophil stimulants, such as factors from macrophages, to the isolated lung and endothelial monolayers and then determine endothelial injury by physiologic, biochemical and (electron) microscopic techniques. In addition to CGD cells, we will also use chemically-generated O2 radicals and O2 radical scavengers to determine the role of O2 radicals. The results will demonstrate if neutrophils or O2 radicals damage endothelial cells and if this damage causes physiologic dysfunction at the organ level. This new knowledge will be applicable to neutrophil or O2 radical mediated acute lung injury and to other disorders which involve a destructive interaction of neutrophils and vascular endothelium.